* configure.in (ARCH_FLAG): __sync_val_compare_and_swap_4 needs
  -march=i486 on at least linux gcc 4.1.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@44953 b2dd03c8-39d4-4d8f-98ff-823fe69b080e